The present invention relates to an apparatus used to test ultrasound transducers. In particular, the device is used to test ultrasound transducers of the type used in medical ultrasound diagnostic equipment.
Ultrasonic transducers are used in the manufacture of scanheads for ultrasonic diagnostic equipment. In a typical ultrasonic diagnostic scanhead, three ultrasonic transducers are used to transmit the ultrasound and to sense the echos used to form the image. The present state of the art in electronics has advanced to the point where a factor limiting improvements in ultrasound units is the ability to match the three transducers used in a single scanhead. If the transducers are not of uniformly high quality, the image will appear to flicker due to differences between the transducers. Unfortunately, it is difficult to characterize transducers in order to match them. Therefore, it is very difficult to get matched transducers. Accordingly, it would be desirable to be able to characterize transducers over their entire surface as well as any point in the acoustic field in order that matched transducers could be placed into a particular scanhead. A device capable of testing transducers could also be used to improve yields and determine the effects which create problems in their manufacture.
Similar types of problems arise in the manufacture of a linear array and phased array transducers. Yet, heretofore, there has been no way to measure the surface vibrational characteristics of ultrasound transducers which were coupled to a medium of the acoustic impedance used in actual operating conditions, e.g., a medium having an acoustic impedance substantially equal to that of water. Various researchers have used laser interferometers to measure the surface displacement of transducers and generate contour patterns. Such techniques are highly complex, very expensive, and subject to numerous inaccuracies. Likewise, existing miniature hydrophone probes employ extremely small active areas to measure the point response in the acoustic field. This typically results in devices which are extremely fragile, difficult to match electrically, and unreliable. Consequently, manufacturers of ultrasound transducers do not generally use such techniques.
Based upon the present need to properly characterize transducers and the absence of any equipment or methodology adequate to perform that function, it would be highly desirable to have a piece of equipment to evaluate the surface vibration of transducers and measure the acoustic field at any point in space.